Gemcitabine (1; marketed as Gemzar®) is an effective nucleoside analogue that is currently approved to treat breast, non-small cell lung, ovarian and pancreatic cancers and widely used to treat a variety of other cancers including bladder, biliary, colorectal and lymphoma.

Gemcitabine's clinical utility is limited by a number of inherent and acquired resistance mechanisms. At the cellular level resistance is dependent on three parameters: (i) the down-regulation of deoxycytidine kinase, necessary for the activation into the phosphorylated moiety; (ii) the reduced expression of nucleoside transporters, in particular, hENT1 required for uptake by cancer cells; and (iii) the up-regulation of catalytic enzymes especially cytidine deaminase that degrades gemcitabine.
WO2005/012327 describes a series of phosphate derivatives of gemcitabine and related nucleoside drug molecules. Among them gemcitabine-[phenyl-benzoxy-L-alaninyl)]-phosphate (NUC-1031; 2) is identified as a particularly effective compound. These compounds appear to avoid many of the inherent and acquired resistance mechanisms which limit the utility of gemcitabine (‘Application of Pro Tide Technology to Gemcitabine: A Successful Approach to Overcome the Key Cancer Resistance Mechanisms Leads to a New Agent (NUC-1031) in Clinical Development’; Slusarczyk et all; J. Med. Chem.; 2014, 57, 1531-1542).

Unfortunately, NUC-1031 is extremely lipophillic and thus poorly water soluble (by calculation: <0.1 mg/mL), and the ionisable moieties, pyrimidine nitrogen and phenolic hydroxyl, have calculated pKa values which lie out-side the pH range suitable for parenteral administration. It is essentially insoluble in water, regardless of salt content or pH, and this has serious implications for the development of clinically acceptable methods for delivering the compound at sufficiently high dosages for effective treatment. Sometimes, the delivery of drug molecules as lipophillic as NUC-1031 can be achieved but only with an unacceptable level of pain to the patient.
NUC-1031 exists as a mixture of two diastereoisomers, epimeric at the phosphate centre:

It is an aim of certain embodiments of this invention to provide a pharmaceutical formulation of gemcitabine-[phenyl-benzoxy-L-alaninyl)]-phosphate which delivers an effective dose.
It is an aim of certain embodiments of this invention to provide a stable pharmaceutical formulation of gemcitabine-[phenyl-benzoxy-L-alaninyl]-phosphate. For intravenous administration, suitable infusion formulations typically should be stable for greater than 30 minutes and up to 48 hours. Typically, for intravenous administration the formulation should be stable both to precipitation of gemcitabine-[phenyl-benzoxy-L-alaninyl)]-phosphate and to degradation of gemcitabine-[phenyl-benzoxy-L-alaninyl)]-phosphate.
It is an aim of certain embodiments of this invention to provide a pharmaceutical formulation of gemcitabine-[phenyl-benzoxy-L-alaninyl)]-phosphate which delivers an effective dose intravenously.
It is an aim of certain embodiments of this invention to provide a parenteral formulation of gemcitabine-[phenyl-benzoxy-L-alaninyl)]-phosphate which can be administered in either a peripheral vein or via a central line. Thus, it is an aim of certain embodiments of this invention to provide a formulation which has an osmolarity which is acceptable for administration via a peripheral vein.
Certain embodiments of this invention satisfy some or all of the above aims.